Intra-articular (IA) antibiotics have been used by equine practitioners for decades when injecting joints in osteoarthritis or to treat septic arthritis. More recently, IA antibiotic usage has gained attention in human orthopaedic clinical practice with the goal of achieving high local drug concentrations in septic arthritis, particularly those associated with orthopaedic implants such as after arthroplasty. In horses, the inability to deliver antibiotics systemically for longer durations without risk of severe side effects (eg gastrointestinal and renal toxicity) has been the impetus to emphasise local vs systemic administration to treat joint infections. Furthermore, the development of biofilms or floating biofilm aggregates in synovial structures may require higher antibiotic doses to penetrate and therefore effectively treat the infection. Finally, antibiotics that would be prohibitively expensive at systemic doses may be administered intra-articularly based on sensitivity results. More rapid resolution of infection through a combination of antibiotic routes of administration (eg systemic, regional limb perfusion and intra-articularly) may also improve owner compliance and convenience in treatment, potentially decreasing cost and complications and improving prognosis with faster resolution of clinical signs compared with long-term administration of oral medications.However, as the IA route of administration is "off-label," appropriate doses have not been defined. Furthermore, the increasing